Microsoft is investigating a widespread service issue causing authentication issues, email delays and failures, and various other issues for Exchange Online customers.
It first acknowledged this incident (tracked under EX1464935 in the admin center) at 5:30 PM UTC, when it began investigating a stream of reports from users on social media.
According to outage tracking service Downdetector, tens of thousands of Exchange Online users are affected and experiencing issues receiving emails via Outlook and accessing the Exchange Online platform.
Microsoft says the list of symptoms includes:
- Delays or failures when sending or receiving email messages.
- Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes.
- Authentication-related errors when accessing Exchange Online services.
- Difficulties accessing or performing actions within Exchange administration experiences.
- Intermittent failures affecting mailbox operations and message delivery workflows.
While the company has yet to reveal which regions are impacted, it has classified this outage as an incident, which is typically used to describe critical service issues with noticeable user impact.
β"We've isolated a common failure pattern across affected Exchange Online requests that is associated with authentication and protocol connectivity," Microsoft added in the latest admin center update.
"We're analyzing service telemetry to identify the underlying source of impact and validate potential remediation options. Additionally, we're continuing to assess the scope of impact and monitor for additional affected scenarios."
Microsoft has addressed multiple Exchange Online outages in recent months, most recently in June, when it mitigated a widespread service issue affecting the mail flow pipeline for customers across North America, Asia-Pacific (APAC), and Europe.
In April, it also resolved Exchange Online mailbox access issues that had intermittently impacted Outlook mobile and macOS users for weeks, and an Exchange Online outage that prevented users from accessing their mailboxes via Outlook on the web, Outlook desktop, Exchange ActiveSync, and other Exchange Online connection protocols.
Update August 31, 14:29 EDT: Microsoft blames the outage on core authentication configuration issues.
"We've identified issues related to a core authentication configuration used by multiple internal services within the Exchange Online infrastructure," Microsoft said. "We're performing a manual test on the individual server level to reset to configurations to validate if this resolves the issue."
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